1. Field of the Invention
The invention relates to a brake control apparatus that controls barking forces that are applied to wheels of a vehicle, and a method for controlling the same.
2. Description of the Related Art
For example, Japanese Patent Application Publication No. 2006-123889 (JP-A-2006-123889) describes a brake control apparatus that is equipped with so-called brake-by-wire technology. According to the brake-by-wire technology, a brake operation performed by a driver is detected, and a braking force that is required by the driver is generated under electronic control. With the brake control apparatus, a cooperative braking control, in which a required braking force is obtained by combining a regenerative braking force with a hydraulic braking force, is executed. Using a regenerative braking force along with a hydraulic braking force improves the fuel efficiency of a vehicle. In the brake control apparatus, paired linear control valves, which are shared by all wheel cylinders, control wheel cylinder pressures in the respective wheel cylinders. In terms of cost performance, providing only one pair of linear control valves is better than providing linear control valves for respective wheel cylinders.
In the cooperative braking control, the brake control mode may be switched from a brake control mode in which the required braking force is obtained only by the regenerative braking force to a brake control mode in which the hydraulic braking force is used along with the regenerative braking force to obtain the required braking force. In this case, some control characteristics of the hydraulic braking force may affect the braking feel felt by a driver, for example, a delay in response of the hydraulic braking force to an operation may give a sense of discomfort to the driver. For example, the rate of change in the vehicle deceleration is slightly decreased temporarily, which may cause the driver to feel that the brakes have become less effective.